The invention relates to a yarn feeding device having a storage drum which stores yarn in windings thereon, a sensor including several movable feeler arms displaceable out of home positions by the yarn windings, a spring assembly which loads each feeler arm towards the home position, and a signal generating detecting device for detecting the position of the feeler arms.
A yarn feeding device having such a sensor device is known from operation and maintenance manual IWF 9 007, IWF 9 107, IWF 9 207 of the company IRO AB, SE, reference number 07-8930-0812-01/9647, pages 10, 43, 44, 50, 51 and 53. Inside the sensor device, two feeler arms are arranged one above the other and such that their feeler feet detect the yarn store for the presence or absence of yarn at two locations in the advancing direction of the yarn windings on the storage drum. Each feeler arm is formed as a wire bracket with two legs. A bent feeler foot protrudes downwardly from the sensor housing. Each feeler arm has its own pivot axis where a sleeve can be clamped which carries an arm prolonging the feeler arm beyond the pivot axis to the side opposite the feeler foot. The end of this arm engages in the detecting device arranged within the sensor housing or at the housing of the yarn feeding device, and at the side of the pivot axis opposite to the feeler foot. Within the detecting device, an opto-electronic switch is provided which generates a signal when shadowed by the arm. A bending spring is anchored to the detecting device and extends in the direction towards the pivot axes of both feeler arms and actuates each arm such that the feeler foot is loaded in an elastic resilient fashion towards its home position, irrespective of the mounting position of the yarn feeding device. The sensor device includes a plurality of components, needs much mounting space in the direction of the axis of the storage drum and in the lateral direction, requires particular care and skill for adjustments, and shows an occasional unstable response behavior in delicate operation conditions.
It is an object of the invention to create a yarn feeding device as mentioned above which is characterized by a compact sensor device including few single parts and having an accurate but insensitive response behavior.
This object is achieved by supporting the plurality of feeler arms with their feeler arm portions on a common axis. The sensor device can therefore be made compact and has only a few components. All of the feeler arms can be placed at essentially the same radial distance from the storage drum. The feeler feet may have essentially the same effective lengths. By a compact arrangement of the feeler arms with essentially equal movement relationships among themselves at the common axis and with the feeler feet of essentially the same length, an accurate but insensitive response behavior of the sensor device can be achieved. Further, the common axis for all feeler arms saves mounting space within the sensor housing.
At least two, preferably even three, feeler arms can be supported on the common axis such that several functions can be carried out by one compact sensor device.
The axis is arranged within the sensor housing where it may be placed at an optimum location. Expediently, said axis is secured without the possibility of rotation while the feeler arms can be pivoted in relation to said axis. However, it is possible to support said axis in a rotatable fashion.
The axis extends essentially laterally to the longitudinal direction of the storage drum axis, the feeler arms are arranged so as to be essentially parallel to the storage drum axis, and the feeler feet are located at different distances from the axis. A shim sensor device is the result which advantageously is received within the bracket of the yarn feeding device. Expediently, each feeler arm portion is only as long as the distance of its feeler foot from said axis. For this reason, said feeler feet can be placed neatly within an axial array.
The axis is oriented essentially parallel to the direction of the axis of the storage drum, while said feeler arms lie laterally with respect to the axis of said storage drum. For this reason, feeler arm portions of equal lengths and equal lever arms for the feeler feet can be realized. Moreover, said feeler feet can be arranged exactly within an axial array along said storage drum.
The spring assembly includes a spring element and a switch-over device which allows adjustment of the spring force if the feeler arm has reached a predetermined stroke position out of the home position. The generation of detrimental vibrations influencing the response behavior is prevented in a structurally simple way. The spring element not only has the task of generating the load for the feeler arm in a direction towards its home position independent from the mounting position of the yarn feeding device, but additionally and without significant structural efforts also dampens the generation of oscillating swing movements of the feeler arm in critical operation conditions, occasionally already in motion. This is achieved by making the spring harder in dependence from its stroke and for a motion range of the feeler arm into which the feeler arm may move due to certain operation dynamics while not detecting the presence or absence of the yarn store. The compulsory damping suppresses an undesirable oscillation effect without influencing the operation of the feeler arm during detection of the presence or absence of the yarn. Vice versa said dampening effect improves the correct operation of the feeler arm within its intended detecting operational range.
The spring suspension of the feeler arm and the above-mentioned damping effect are achieved in a structurally simple way, in that the spring element is a freely ending bent spring which actuates the feeler arm portion, and at the side of the spring element opposite the feeler arm a damping boss is provided and constitutes the switch-over device.
Since the detecting device and the spring assembly are integrated into the sensor housing at the same side of the axis like the feeler arm portions carrying the feeler feet, considerable mounting space is saved in the direction of the axis of the storage drum. Moreover, the number of single components of the sensor device is reduced. Mounting space also is saved lateral to the axis of the storage drum since the respective, co-acting parts can be arranged close to one another. This is of advantage for a sensor device having several feeler arms and correspondingly many accessory parts. Thanks to the compact arrangement, detrimental vibrations are prevented so that a stable but nevertheless sensitive response behavior is achieved.
Since the detecting device faces the spring assembly via the feeler arms operating in between, space can be saved.
The feeler arms extend beyond said axis feeler arm portions which cooperate with the detecting device and/or the spring assembly. In this case, more mounting space might be needed in the direction of the axis of the storage drum. However, the detecting device then is protected against contamination and lint.
The feeler arm portions are of different lengths to achieve at least substantially similar lever relationships and motion relationships when detecting the position of the feeler arms despite the different distances of the feeler feet from the common axis.
The feeler arm portions are formed as ballast masses or are equipped with ballast masses. A weight balance is achieved by said masses. Said weight balance protects the yarn against undesirable strong mechanical loads.
The detecting device is arranged outside the sensor housing on a printed circuit board. The feeler arm portions of the feeler arms extend beyond the common axis and reach towards the detecting device and are protected against contamination while co-acting with the detecting device. In addition, the prolongated feeler arm portions result in a weight balance which is more wear resistant and, for this reason, heavier feeler feet can be used.